I hardly do any privates, but in the past whenever anybody would request one I would decline and PM them to find out what they want first. I did that really because I wasnt willing to do a lot of what other girls do (though I pretty much will now), and I wanted to make sure they knew what they were going to get for their tokens. 99% of the time they would then change their mind.
Though now Im decided that if someone does that again, fuck it. Especially if its someone Ive never seen around before, or hasnt ever talked to me. I have it clearly written in my profile what my privates entail, if theyre too lazy to read it then thats their problem. Ill accept the private, then going about what I normally would do and find out what they want. If its something I wont do, Ill tell them. If they get upset, Ill point them to my profile.